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Updates on HIV testing Window Period

27th June 2013 was National HIV Testing Day in the US.

There were a lot of activities to promote HIV testing.

What I found interesting and also should be of interest to many readers of this blog is the HIV Testing Factsheet published by the CDC.

HIV Signs and Symptoms

The HIV Window Period and Test Accuracy

HIV PEP Post Exposure Prophylaxis

Please allow me to highlight some points in this factsheet:

1. The factsheet says that antibodies to HIV typically develop between 2 to 8 weeks after exposure to the virus. This we already know but I am glad there is more official recognition of this fact. So for those of you who are still sweating over your 3 months HIV test, stop sweating.

2. The factsheet also states that the P24 antigen can be detected within 4 to 7 days before antibodies appear. In other words, as early as 1 week from infection. This should also give comfort and reassurance to those of you who have undergone the Combo/Duo test at 3 to 4 weeks from exposure.

3. The factsheet also states that an RNA test can detect the HIV virus 10 to 15 days after exposure. I personally think that this should be the standard of care. Unfortunately, the RNA test in Singapore is costly and has a very long turn-around time. Our clinic in Thailand will be able to run this test at less than half of Singapore’s cost with a 1 to 2 days turnaround time.

Overall, I hope this factsheet published by the US CDC which is easily the most conservative medical institution I know, will give everyone some relief and reassurance.

Click on the picture for the latest information on the HIV testing Window Period

Click on the picture for the latest information on the HIV testing Window Period

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About Dr. Tan
Dr. Tan graduated from the National University of Singapore in 2001. His residency was in the two largest public hospitals in Singapore; Tan Tock Seng Hospital and Singapore General Hospital.

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  1. I had a needle prick (really small one) in year 2016 around November period. This needle was used and the source is unknown. Then I went to do hiv test. It turns out to be negative. And I did the hiv test on September 2017 and it was negative again. I thought I could move on but my back started feeling itchy on April 2018 after I went for Gua Sha. And I went to see the doctor. Doctor gave me antibiotics. I ate one course, the antibiotics did not recover. Then i went to see the doctor again. Then the doctor gave me another round of antibiotics. I finished, but my back still feels itchy….

    So I am really afraid that it is because of HIV that my immune system became low…. and thus the antibiotics is not working…

    So, I went for a hiv ag/ab test conducted by quest lab in September 2018 It turns out to be non reactive…

    I want to know if my back itch (for 6 months) and not recovering is because of HIV. 🙁

    Please help!!!

    Super super worried

    • Clearly your symptoms are not due to HIV. There are a hundred other things which can cause an itchy rash. Please visit us for a proper evaluation.

  2. Samantha

    Hello Dr.,

    I had a possible exposure on May 7th where I am unsure if he ejaculated in the condom. On May 23rd, I took a 4th gen test fingerprick test that was negative. That was 16 days post exposure. I then took an oraquick oral swab test at 7 weeks and it was negative. I then took an oraquick advance oral swab test at 8 weeks and it was negative. Am I conclusively negative? Or should I still worry and take another test? I would very much appreciate your advice from your experiences with these tests. Thank you

    • I would consider your exposure risk low, and your current test results a very good indication. However, for conclusive testing we would advise a 4th generation test at 28 days or more post exposure, or a 3rd generation test from 3 months or more. The oraquick tests are 3rd generation test kits.

  3. raj kumar


    i had a massage recently at massage parlor with hand job service.

    NO blow job, NO vaginal sex, NO oral sex, NO anal sex.

    It’s just during the 3 minutes body to body massage [only at upper back], the therapist was naked and her private part touched only my back [center of spine]

    i am quite worried.

    subsequently I had CMIA 4th gen test done on day 7, day 14 and day 16 – all test was -ve .

    should i proceed with HIV RNA test at your center?

    • There is no risk from this exposure, so I do not believe RNA testing is necessary. Of course, if you are concerned it is always best to visit us in person for a proper consult and evaluation.

  4. DR.Tan I have tested negative on day 87 after exposure using the 3rd gen rapid test should I retest after 6 month because some of the guidelines said that window period for 3rd gen is 3-6 months? is my test conclusive?

  5. Jharden

    Hello, i have a question about hiv and hep c coinfection window period.

    Is it true that hiv and hep c infection from the same exposure would delay seroconversion.

    I ask this because recently i had been exposed to a hiv+ blood but unknown of his hep c status, but i suspect that he does has hep c. The exposure risk was the blood was in contact with my wound (3-4 days scrapped/ no scab)

    And i have tested negative for hiv at 45 days and 84 days using 3rd gen elisa and 4th gen rapid prick test respectively.

    Thanks in advance.

  6. Hello dr, is rapid prick combo test at 84 days conclusive following a low risk exposure? Is the 3 months 90 days or 84 days? How much faith can i put on a 84 days negative result with rapic prick combo test with percentage 0-100%?

    • Dr. Julian Ng


      Generally, if the test you did was a 4th generation HIV Combo rapid test and it was done 28 days after exposure, it is conclusive.

      • Even if it was 84 days post exposure? I thought p24 antigen would drop after 6 weeks? And could it be my antibodies are still not developing? Thats why its negative? Pls answer here, really need your guide here

      • Help dr, please reply my answer as there are many confusing information i found. Thanks in advance

  7. ChellJones

    Hi doctor. I had a 60 second finger prick test a 6 and 8 weeks, bother were negative. Should I still worry?

    • If it was a 4th generation combo test, I would consider the tests conclusive. If it was a 3rd generation antibody-only test, then you would be advised to repeat a test at 3 months post exposure.

  8. Dear doctor
    I had a needle exposure. At 87 days Rna pcr for Hiv 1 is not detectable. At 102 days result is antibody 0.06 and antigen not detected(non reactive) . At 196 days result is antibody 0.00 and antigen is 0.02(non reactive) (Cut off 0.25). I have oral lukoplakia now which is not going. Sometimes my nerves shiver and little pain in groin area and ear leaf. Test are done by Mini vidas method. Could you Sir help me to understand the Hiv result and what causes the problem. My AEC is 186. Kindly help my marriage is on coming April. Whether there is chance for Hiv 2.

    • I would consider your tests conclusive. The 4th gen testing is for both HIV-1 and 2 so please relax and move on with your life.

    • SANDIP C

      Dear doctor
      Thank you for your kind reply. I am facing now pain in lymph nodes area. I got black spots in my back. Red spots in my legs. Two questions I have for you Sir.

      1. As my 102 days result was antibody 0.06 and antigen not detected and 196 results is antibody 0.00 and antigen 0.02. I have no exposure in between. Whether there is any chance left that it could reach at any time at the limit 0.25? My Hep b result is 0.01 at 196 days(limit 0.13).Hep C non reactive at 196 days.
      2. What further test do I need to diagnose problem. Whether 6.5 months testing valid for all cases. Kindly help Sir.

  9. Hello sir
    I have read many specialist say that the 4th generation tests are conclusive after 28 days. But i have also read on some studies saying that there is another window period where antigens and antibodies are both low and 4th generation cannot detect them and they are talking about after the antigens are detectable. So in that case they are saying 4th genertion tests cant detect for a short time during second window period.
    Then i saw this FDA study for 4th generation test where it says that latest someone came reactive was 78 days. Air how can both antigens and antibodies stay undetected till day 78 ? Sir kindly read it and explain this to help out many in depression. I am sharing the link sir

  10. Hi Doc,

    I had a condom break incident with a CSW 30 days ago. I tested with the Alere HIV Combo rapid kit at 18 and 26 days. Both results were negative. I had mild flu like symptoms on the 15th day including fatigue,malise and rashes on my shoulder and back. It is day 30 today and I still have rashes coming and going on my body. I also have developed insomnia from day 15. I sleep for 3 or 4 hours before I wake up and have bad sleep till the morning. My question is, is this a common symptom ? Can I take confidence in my 26 day rapid test ? I confirmed that it is the latest alere HIV combo test and not the Alere determine test.

    • I believe your tests are sufficient, however if you are keen for conclusive results then you will have to repeat 28 days or more post-exposure.

  11. Hi Doctor,

    After 3 months of my extreme risk unprotected exposure(with positive women),i did my health screening and got very bad results.

    My CD4 count is 225(margin: 200) and CD8 count is very much higher than it.

    Doctor asked me, if you had any hiv or viral related infection in last 3/6 months.
    Then i said yes(unprotected with positive women). He asked me to run RNA PCR test to know the viral load. Since your immune is going very weak.

    My Hepatitis A is positive (6 months before i tested it was negative), then i have asked that women and she said, she has HAV as well. so now i’m got it from her.

    She doesn’t had HBV,HCV and me as well.

    He adviced me, once you get undetectable viral load result, Try to get tested every month till you reach 12 months.
    Due to your slow/weak immune system, it will take more time to response to HIV. Even it will response quickly the production of antibodies will be very slow. That couldn’t able to detect by Antibody tests which you did (HIV 1/2 – 3rd generation ELISA test).

    After my week of exposure, i have got extreme dry cough with mild fever and heavy cold, conjuctivitis. Still i have sore/strep throat (100 days over) with white tongue, swollen lymph nodes(never had in my life) under my right neck ear with pain. I never had this much long illness from my childhood.

    I found more blood is going through urine by Urinaysis test.
    I have fordyce spots in my penis/lips(i never had in my life).

    My weight in July 2nd week is 68 but right now it is 62 with extreme tiredness, fatigue and joints pain.

    Can i assume that i’m, affected but due to weak immune system, my body is producing antibodies very slowly?

    Shall i follow my doctor’s advice to run RNA PCR (it is accurate after 3 months of exposure)?

    • 1. Many acute illnesses can cause CD4 count to drop transiently.
      2. Hepatitis A is not sexually transmissible – it is an acute infection from eating contaminated food, and you would not regularly test for acute hepatitis A infection, only for hepatitis A antibodies which just indicate a past infection or immunity from previous vaccination.
      3. I believe your HIV antibody tests are conclusive.
      4. If you still wish to do HIV RNA PCR then go ahead.

      • Hi Doctor,
        I had unprotected exposure with hiv positive women and after 100 days I have took hiv 1/2 antibody test and it’s negative but new hiv related symptoms are keep coming. Now I have got night sweating, joints paining, red rashes, sore throat, weight loss, nail Color changing to yellow with thickening and mouth ulcer(I never had in my life).